1. Field of Invention
This invention relates to microphone and speaker devices associated with a telephone for allowing a user to listen and speak in duplex mode. More particularly, the present invention relates to a speaker and microphone combination which can be positioned at the ear of the user to enable hands-free communication over the telephone.
2. Prior Art:
The conventional telephone device utilizes a handset which includes both the microphone and speaker positioned at opposing ends in a spacial relationship which locates the speaker at the ear of the user and the microphone near the mouth of the user. The speaker portion of the telephone handset includes a cupped section which isolates the speaker sound and shields it from transmission beyond the ear when positioned against the user's head. Accordingly, the microphone portion of the handset does not detect transmitted sounds from the speaker because of its separated position from the speaker at a distance of three to ten inches, as well as a shielding effect from the cupped configuration for the speaker casement.
This acoustic isolation between the microphone and ear speaker are critical for several reasons, including the avoidance of feedback. Acoustical feedback occurs when the acoustical vibrations received at the microphone include both sound generated by the voice of the user, as well as ambient sound vibrations which include the same voice or vibrations transmitted through the speaker. Amplication of the voice signal and transmitted sound signal are amplified repeatedly and generate the accustomed squeal which characterizes the occurrence of feedback. The most common occurrence of feedback is when an individual holds the microphone near a speaker which is broadcasting the very sounds which the microphone detects. It is well known that an individual speaking through a microphone must separate himself from any of the speakers broadcasting the amplified sound.
The conventional telephone device creates an even greater risk of feedback because of an included side tone which enables the user to hear his own voice through the ear speaker the same as the remote party hears his voice through a telephone line. Specifically, this side tone is split off from the actual electronic transmission of the speaker's voice through the telephone device. This split off signal is routed to the ear speaker for transmission to the user. In actuality, therefore, the user hears the full conversation through the ear speaker, including both the remote signal generated by the other telephone user and the original signal transmitted from the first user's telephone.
Because of this side tone, placement of the ear speaker in proximity to the microphone component potentially generates feedback signal in the same way that the microphone of a PA system held near its output speaker will result in feedback squeal. For this reason, headsets applied to telephone devices have utilized a boom to displace the microphone to the vicinity of the mouth and away from the speaker element of the headset. In addition, sound insulating foam or other materials is cupped around the ear microphone component to prevent transmission of sound, including the side tone, from being picked up from the microphone. Practically speaking, this separation distance must be at least two centimeters, and is generally preferred to be at least five centimeters. This is the case with conventional handsets, as well as all headset-type telephones.
In the case of headset-type devices, the inconvenience of having the microphone boom projecting in front of the user's face is difficult to overexaggerate. Those who have required use of a hands-free telephone system are well experienced with the disadvantages. For example, various objects brought near the face may catch on or strike the boom, tearing it from the headset or otherwise creating sudden striking sounds in the ear of the remote listener. The terminal end of the boom tends to catch on clothing and various other obstacles at the most inappropriate times. Aesthetically it detracts from the user's appearance, and therefore has prompted development of creative means of concealment when used with television and other media applications.
Nevertheless, in absence of an acceptable alternative, the headset with projecting boom remains the dominant device for hands-free telephone communication or electric voice transmission in general.
In fact, the broadcast industry in general utilizes the same side tone technology as is used in the telephone system to permit the user to hear his or her own voice in a manner similar to that which the audience hears through a PA system. Accordingly, the same technical limitations arising from feedback apply in the broadcast industry, as they do to telephone communications.
What is needed is a device which eliminates the need for the user of a microphone boom and somehow permits location of all microphone and speaker elements within an earpiece capable of being positioned or suspended at the ear of the user.